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I've got an SG503 on my bench that seems to be working fine on all ranges with nice leveled output, etc. However, the finger contacts under the cam switch need to be cleaned as I have to fiddle with the switch a bit to make contact at some settings.

It is my understanding that the best way to clean the finger contacts is to get a piece of paper/cardstock with a bit a 99% isopropyl under the contacts and gently pull it across the contacts. For those who have done this before, my question is what is the best approach to do this with a SG503? Is there a way to do this without a major disassembly? I'm not adverse to disassembling the module but I don't wan't to overcomplicate things if I don't have to.

Thanks!
Jay

Looking at the service manual, it looks like the fingers on the cam side would be in the open position between switch detents. I'm thinking I can carefully slide a piece of paper in between the fingers when the switch is in between detents. I'll give this a try later. Any suggestions in the meantime would be appreciated.

Alright, I answered my own question. It looks like you can easily get at the finger contacts from the side of the switch that is next to the big vari cap. I was easily able to get a piece of paper under the contact , close the contacts and clean them in all the positions. The switch is working much better now.

A question for the next time I need to clean Tek finger contacts, is there a recommended 'type' or thickness of paper to clean the contacts? I used whatever garden variety paper that I had on my bench (laser printer paper).

I can't answer that question (I'm sure others can), but ISTR that the paper
cleaning method should not be used on some TM-5xx(x) plug-ins.

DaveD
KC0WJN


On Sat, Apr 19, 2025 at 13:11 Jay Czaja via groups.io <jmczaja=
[email protected]> wrote:

A question for the next time I need to clean Tek finger contacts, is there
a recommended 'type' or thickness of paper to clean the contacts? I used
whatever garden variety paper that I had on my bench (laser printer paper).

Interesting, I wonder why that is? Obviously contact cleaner wouldn't be a great idea for these type of contacts but I'm curious why paper wouldn't be recommended. Too abrasive?

Your problem might not be dirty contacts. I recently found that my cam barrel had deteriorated and actually had shrunk. The end of the can barrel serves as a bushing that fits into the mounting bracket. The diameter of the bushing was smaller by more than 0.01 in ( 10mils). Consequently it was too loose. In addition, the cam lobes were also smaller in height. With the overall diameter shrinkage, the bushing was loose and the cam lobes were not applying sufficient pressure to make firm contact. Fiddling with the knob to make contact is a clue that the cam barrel is loose fitting.

Thankfully, cleaning seemed to have done the trick in my case. No more flashing 000's and the switch works in all positions.

I don't remember which plug-in(s) was (were) cited, or what the reason was,
but I do remember being surprised.

I need to write this stuff down when see it.

The comnent that I read was probably on one of the TekScopes, TekScopes2 or
tek500 forums.

DaveD
KC0WJN


On Sat, Apr 19, 2025 at 13:33 Jay Czaja via groups.io <jmczaja=
[email protected]> wrote:

Interesting, I wonder why that is? Obviously contact cleaner wouldn't be a
great idea for these type of contacts but I'm curious why paper wouldn't be
recommended. Too abrasive?

On Sat, Apr 19, 2025 at 01:14 PM, Dave Daniel wrote:

I can't answer that question (I'm sure others can), but ISTR that the

paper

cleaning method should not be used on some TM-5xx(x) plug-ins.

If I remember it properly, the SC504 has a very odd switching mechanism, not really fingers but a conductive elastomer.? The scope was originally spec'd to go to 100 MHz, but the contacts limited the bandwidth.? It's a rather fragile and picky switch, and I remember reading that it had very special cleaning instructions (if at all).

Harvey

The cardstock that I use is Vellum Bristol. Neenah Exact Vellum Bristol, specifically, and I picked up a bundle of it at Sam’s club a few years ago. Most office supply stores will probably have something similar and sufficient. I’m not saying that I know that to be Tek spec, but I’ve only seen recommendations FOR and not against using vellum bristol cardstock.

On Sat, Apr 19, 2025 at 11:10 AM, Dave Daniel wrote:

why paper wouldn't be recommended

Generally, paper vendors ... like for copiers, or laser printers... won't tell you what is in their paper, or what is on the surface of their paper.
At least, they won't tell me.
AFAIK... and at least... a lot of paper... has 'clay' as a binder... and, 'ink jet printer paper' may be 'coated' with some kinds of 'clay'
Of course this 'clay' ... whether used as a binder, in the paper... or as an ink 'stabilizer' ... when coated on the surface of the paper... is a highly refined material.
Yet... just by the vary nature of the minerals that clay is composed of... there is an abrasive content.
Does that content, significantly abraid the gold on contacts.
Who knows?

--
Roy Thistle

graphic papers (for printing) will contain clay as it's made and in coating
after it is made, it most likely will have calcium carbonate to combat acid
degradation over time of the wood fibers and for brightness, titanium
dioxide is also used for opacity and brightness. All 3 of these "pigments"
are abrasive clay the least, Ti02 the most. There are all kinds of graphic
papers that may or may not contain these pigments, may or may not be
precoated, top coated, and calanderd. I would not use any paper to make
strips for cleaning leaf contacts once wet is likely to "shed" all kinds of
stuff. Plain uncolored card stock is ideal with no pigments, heavy and
stiff and not wilt when soaked with IPA, I use those tags with a string
attached for IDing stuff, easy to cut thin strips, soak with IPA, slide
under open leaf and then close to "lock" the strip as I pull it out to
scrub the contact surface, firm but gentil

On Sun, Apr 20, 2025 at 1:47?PM Roy Thistle via groups.io <roy.thistle=
[email protected]> wrote:

On Sat, Apr 19, 2025 at 11:10 AM, Dave Daniel wrote:

why paper wouldn't be recommended

Generally, paper vendors ... like for copiers, or laser printers... won't
tell you what is in their paper, or what is on the surface of their paper.
At least, they won't tell me.
AFAIK... and at least... a lot of paper... has 'clay' as a binder... and,
'ink jet printer paper' may be 'coated' with some kinds of 'clay'
Of course this 'clay' ... whether used as a binder, in the paper... or as
an ink 'stabilizer' ... when coated on the surface of the paper... is a
highly refined material.
Yet... just by the vary nature of the minerals that clay is composed of...
there is an abrasive content.
Does that content, significantly abraid the gold on contacts.
Who knows?

--
Roy Thistle